The invention relates to fingerprint coding and recognition and retrieval systems based on generally invarying topological irregularities, characteristics or minutiae (which terms are used interchangeably herein) of fingerprints. The term "fingerprint" or "print" is used in reference to the epidermal ridge lines of the ten fingers of the human hand, palm prints, toe and sole prints of humans wherein such epidermal ridge lines and characteristic features thereof are in patterns unique to a particular individual.
In my U.S. Pat. Nos. 4,747,147 and 4,817,183 and my papers entitled "Digital Coding of Single Fingerprints--A New Approach for the Computer Age", Journal of Police Science and Administration, Vol. X, No. 2, June 1982, (1) "A TOPOLOGICAL APPROACH TO THE MATCHING OF SINGLE FINGERPRINTS: DEVELOPMENT OF ALGORITHMS FOR USE ON ROLLED IMPRESSIONS", NBS Special Publication 500-124, May 1985, and (2) "A TOPOLOGICAL APPROACH TO THE MATCHING OF SINGLE FINGERPRINTS: DEVELOPMENT OF ALGORITHMS FOR USE ON LATENT FINGERMARKS", NBS Special Publication 500-126, October, 1985. I show that the soft elastic nature of human skin causes substantial variation of the spatial descriptions of successive impressions of the same fingerprints. Consequently, spatially based coding schemes used for forming machine searchable databases have inherent inaccuracies due to the fact that the spatial based coordinate system typically used for coding purposes could not take into account the wide variations in spatial distortions making the match or identification between two rolled prints on the same finger somewhat problematical particularly where the prints are taken at substantially different times or pressures.
Topological coding schemes provide concise digital codes that provide a more reliable basis for fingerprint identification systems. In my above referred to patents and paper, I disclose comparison methods based on topological coding of prints in which a topology base coding system for recording and comparing minutiae used a single vector array generated from topologically based coding of a fingerprint.
In the topological vector extraction part of the system disclosed in my above referred to patents, 1982 Paper and my NBS Special Publication 500-124, the core of the fingerprint is centrally located at a reference point and a horizontal line is projected through the core to intersect ridge lines to each side of the centrally located reference point. In the case of an arch a vertical line is drawn through successive ridge summits. From the points of crossing of the ridges with the projected horizontal or vertical line, the ridges are traced to the first significant irregularity and a type code (T) is assigned to the irregularity. In my patents, the distance (D) from the reference line is measured and these data are recorded in a predetermined order to constitute a topological vector for the print which then is recorded in a machine searchable database. Comparison of vectors takes the form of a sequence of array operations. Comparison of good quality rolled prints is performed extremely rapidly on this basis. In my NBS Special Publication 500-126 I disclose a system for topologically coding fingerprints wherein each topological code would be a vector generated by exploration from short straight lines orthogonal to ridge flow direction and drawn offset from a given characteristic (bifurcations suggested).